Programmable integrated circuits (ICs) are often used to implement digital logic operations according to user configurable input. Example programmable ICs include complex programmable logic devices (CPLDs) and field programmable gate arrays (FPGAs). CPLDs often include several function blocks that are based on a programmable logic array (PLA) architecture with sum-of-products logic. A configurable interconnect matrix transmits signals between the function blocks.
One type of FPGA includes an array of programmable tiles. The programmable tiles comprise various types of logic blocks, which can include, for example, input/output blocks (IOBs), configurable logic blocks (CLBs), dedicated random access memory blocks (BRAM), multipliers, digital signal processing blocks (DSPs), processors, clock managers, delay lock loops (DLLs), bus or network interfaces such as Peripheral Component Interconnect Express (PCIe) and Ethernet and so forth. Each programmable tile typically includes both programmable interconnect and programmable logic. The programmable interconnect typically includes a large number of interconnect lines of varying lengths interconnected by programmable interconnect points (PIPs). The programmable logic implements the logic of a user design using programmable elements that can include, for example, function generators, registers, arithmetic logic, and so forth.
CLBs within FPGAs can include one or more look-up tables (LUTs). LUTs can be used to implement various combinatorial functions and other logic elements. For large combinatorial functions, many LUTs can be used, requiring LUT-to-LUT connections. LUT-to-LUT connections can be made using the programmable interconnect of the FPGA. However, use of the programmable interconnect can be expensive in terms of resource usage and performance.